Where to put a third TM battery

You might want to consider using a Trollbridge by Yandina instead. The first thing I did when I bought my new Puma a few days ago was have the 3 bank charger removed and replaced with a one bank and have the Trollbridge installed. When I run the big motor, my trolling motor batteries are being charged. This eliminates the weight of the extra battery and the 3 bank charger. I used this on my last boat and never ran out of power on windy days. When I plug in my charger after fishing at days end, the one bank charger almost always shows that I have a full charge already. By the way, you can also have the Trollbridge connected to your tow vehicle to charge your batteries while youre towing. I havent done this, however. Mine is just connected to the alternator in my Merc Pro XS. Heres a link. http://www.yandina.com/

Follow Sam Rushs idea on this one. Install a “bridge” across the sump area. I had aluminum diamond plate across mine, but anything similar should work just fine. Secondly, DO NOT SKIMP on the batteries you choose. In years past we were so concerned with our T/M battteries and thought little of the cranking battery, provided it had enough power to meet or exceed the engine manufacturers recommendation. Now though, with the improved aeration, color graphs and GPS combo units front and rear, the cranking batteries get a real work out. Get the largest batteries you can get all around. The BCB aluminum battery trays are awesome as well.